The specific objectives of these investigations continue to be directed toward evaluating the role of regional lymph nodes (RLNs) in systemic immunity. Our observations demonstrated that cytotoxicity of a macrophage is derived from its ancestral bone marrow stem cell. The possibility is considered that the direction of stem cells toward production of cytotoxic macrophages is mediated by RLN cells. The proposed studies aim at clarifying the role of RLN cells in the development of specific cytotoxic macrophages and to further substantiate or repudiate the concept that macrophages in a tumor-bearing host are cytotoxic at "birth" rather than that they must gain that property through "activation". These investigations will determine (a) temporal relationship of occurrence of cytotoxicity in RLNCs, bone marrow cells (BMCs) and macrophages; (b) necessity for presence of RLNs in a tumor-bearing host for initiation and maintenance of macrophage cytotoxicity; (c) ability of transferred sensitized RLNCs to initiate production of cytotoxic macrophages by bone marrow of normal mice; (d) effect of antitumor treatment on RLNs and whether alterations produced affect cytotoxic macrophage production. A second series of investigations will relate to the significance or lack thereof of the cytotoxic macrophage in the control of primary and metastatic tumor growth. Those studies will (a) ascertain the relationship between dissemination of tumor cells from a primary tumor and its macrophage content; (b) compare macrophage content of a primary tumor with its metastases; (c) compare macrophage content of primary tumors of animals developing metastases with those who do not; (d) determine effect of removal of a primary tumor with or without RLNs on macrophage content of metastases; and (e) ascertain if the site of a metastasis influences its macrophage content. Additionally, macrophage depletion and/or functional alteration on growth of established primary tumors and incidence and growth of metastases and the influence of an effective chemo-immunotherapeutic regimen on macrophage content of primary and metastatic tumors will be studied.